Red Copper vs Dwarf Shield

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Dwarf Shield is a little darker, warmer than Red Copper.

Can I use Dwarf Shield instead of Red Copper?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Dwarf Shield is a little darker, warmer than Red Copper.

Can I use Red Copper instead of Dwarf Shield?

The same difference applies the other way round: Red Copper is a little lighter, cooler.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.